This project is primarily concerned with furthering our understanding of the relations between physiological aging processes and specific diseases in the elderly. The major focus is on glucose homeostasis and diabetes mellitus. Studies are directed at long-term follow-up of volunteers in the Baltimore Longitudinal Study of Aging in order to acquire actuarial data for judging the significance of varying levels of performance on the diagnostic tests for diabetes mellitus which are in clinical use. Other studies are directed at discovering the patho-physiologic mechanism underlying the age changes in performance on these tests. Serum cholesterol levels have been measured longitudinally since 1963. In addition to the effects of aging (a tnedency to rise in the early adult years and to fall in old age), there have been secular trends towards a general increase in level until 1971 followed by a fall thereafter. These recent changes are coupled with nutrition changes in these subjects: lower fat intake, lower saturated fatty acid intake and higher polyunsaturated fat intake.